1. Field of Invention:
A textile product providing a normal textile material having one face layer that is convertible by flux of heat into a solid charred fire block layer even at temperatures up to approximately two thousand degrees farenheit.
2. Description of Related Art:
All too commonly a fire may begin when a cigarette falls onto upholstery or into clothes as a person falls asleep holding a burning cigarette. A cigarette, of course, is designed to sustain steady smoldering combustion. The cigarette continues its smoldering combustion where it falls. Sometimes the cigarette continues to smolder for hours, filling the house with toxic vapors. At other times the smoldering cigarette changes into flaming combustion. With an open flame to heat up adjacent objects to their ignition temperatures, the second phase--the phase of exponential growth--begins. Exponential growth begins more quickly during such occurrences as airplane crashes. Burning of seat cushions beneath textile covers adds to quick exponential growth the presence of overwhelming amounts of toxic gases.
When it comes to doing something to prevent or halt catastrophes that occur from exponential growth of fires, measures have been taken in part by recognizing that portions of our surroundings are combustible and add fuel to a fire. The fact that the environment of a house or airplane is combustible does not persuade people to dispense with the amenity of the clothes they wear, the bedding in which they spend a fourth of their lives, the drapes at the window, the chair and desk in the den, the upholstered furniture in the living room or in the plane cabin in exchange for wearing asbestos clothing or sitting on ceramic or metal chairs. The gypsum materials in the wall and the ceiling will not burn, but the wallpaper will and molding will. The frame of the house is wood, the roof is wood, perhaps with asphalt shingling, and the exterior is probably wood, at least in part. An airplane includes plastic ceiling, seat cushions and walls. The structures could, of course, be made safe from fire, in much the same way as the stone, brick, and concrete of many of the multiple-occupancy dwellings in the cities or metal materials used in many military aircraft. Even today the contents of the structure a airplane remain as combustible as before.
1. The material properties of the instant invention depend upon density, total heat content, heat capacity, thermal conductivity, chemical analysis and heat of gasification.
2. Behavior of samples in fire tests depend upon ease of ignition, rate of heat release, rate of surface flame spread, rate of smoke release, rate of toxic gas release and radiant power from flame.
3. Critical survival variables in a burning dwelling or aircraft include temperature vs. time, smoke particulates vs. time and toxic gas vs. time. The time it takes for fire to spread and engulf a structure and for toxic gases to spread therethrough is proportional to the impact on life and health of persons inside.
Inherently fire-resistant polymers have been fashioned for use in the clothing of people whose occupations expose them to the hazards of fires. The more familiar polymers, natural and synthetic, in common use for clothing, house and airplane furnishings such as appliance housings and furniture made of molded polymers may be upgraded for fire resistance. The strategy is to add to the polymer--in its synthesis or by impregnation or by coating--certain elements that share the curious property of interfering at one stage or another in the chemistry and physics of combustion. Principal among these are phosphorus, antimony, boron, chlorine, and bromine. The phosphorous compounds act by alterning the decomposition of the fuel. For cellulose the mechanism is well known. The phosphorous compound decomposes in the heat of the fire to form phosphoric acid, which then reacts with cellulose to produce large amounts of carbon char, at the expense of the reactions that normally would generate combustible gases. Such treatment makes a material hard to ignite with a small ignition source. The reactive halogens, chlorine and bromine, function in the chemistry of the flame itself as "radical poisons," terminating radical chain reactions that occur in the flame. The compound containing the halogen first vaporizes and then decomposes to intercept radicals essential to the propagation of the flame reactions. An example is the removal of a hydrogen free radical by a bromine compound: EQU RBr+H..fwdarw.HBr+R.
In this reaction the sluggish organic fragment, R., replaces the hydrogen radical.
The cellulose textiles, cotton or rayon (from wood pulp), are most often treated with phosphates or borax-boric-acid mixtures. To secure resistance to water in laundering, the phosphorous may be locked into the cellulose by reacting the cellulose with a phosphorous-containing compound or, in the synthesis of rayon, by polymerizing the monomer with a phosporous-containing monomer. This technology is employed in making textiles for children's sleepwear, which is almost the only protective measure established by the upsurge of national concern about fire at the beginning of the last decade.
For the protection of people textiles are now available made of inherently fire-resistant synthetic-polymer fibers. The materials are expensive, and they do not make up into attractive fibers for everyday wear. They serve well, however, in coveralls, flight suits, and uniforms, and they have a record of saving their wearers from calamity.
One family of fibers, marketed as the aramids by the DuPont Company, consists of aromatic (benzene-ring-containing) versions of nylon, such as DuPont's NOMEX.
Nylon melts easily (and can cause severe burns by so doing, without burning) and burns with the help of sufficient heat from a fire. The aramid fiber does not melt or burn, but chars and stiffens.
Whereas the aramid fiber has a hydrogen on its nitrogen, offering oxygen a site of oxidative attack, another structure--the aromatic imide polymer--does not. Exposed to direct flaming, it shrinks and blackens but is not consumed and does not produce much smoke.